GB2568168A

GB2568168A - Relay device

Info

Publication number: GB2568168A
Application number: GB1818272.5A
Authority: GB
Inventors: Takahashi Katsuyoshi
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2016-06-22
Filing date: 2016-06-22
Publication date: 2019-05-08
Anticipated expiration: 2036-06-22
Also published as: JP6355880B2; JPWO2017221357A1; WO2017221357A1; GB2568168B; GB201818272D0

Abstract

A storage unit (191) stores a relay table associating transmitter addresses, relay message types, and destination ports with one another. When a frame including a transmitter address and a message has arrived at one of a plurality of communication ports (904), a frame analysis unit (110) acquires, as an analysis message type, the type of the message included in the frame. A relay determination unit (130) selects, from the relay table, one or more destination ports associated with the combination of the transmitter address included in the frame and the relay message type identical to the acquired analysis message type. The relay determination unit then selects, as a transmission port, each of the selected one or more destination ports except for reception ports.

Description

Title of Invention: RELAY DEVICE

Technical Field [0001] The present invention relates to a relay device such as a bridge.

Background Art [0002] In control networks used in systems such as air-conditioning systems, in order to deal with an expansion in system size and an increase in communication volume along with an increase of system functions, bridges are installed or monitoring is performed for suppression of bandwidth resource.

[0003] In a system using a control network, request messages and response messages are often exchanged periodically so that devices connected to the control network can monitor each other about their states. For this reason, as the number of devices increases, the number of messages for state monitoring also increases, which tends to consume bandwidth resource.

[0004] Bridges judge whether relay of a frame is needed or not for each destination address and do not relay a frame to an unnecessary range. This makes it possible to reduce used bandwidth. Such a bandwidth reduction method is called a bridge method.

Patent Literature 1 discloses an example of a bridge.

[0005] IGMP is specified in RFC 1112 of IETF.

IETF is abbreviation of Internet Engineering Task Force.

RFC is abbreviation of Request For Comments.

IGMP is abbreviation of Internet Group Management Protocol.

[0006] In IGMP, when a querier of multiple queriers sends a query request and a listener sends a report response, other queriers receive the report response and do not send a query request by themselves.

In IGMP, queries and reports are multicast.

Meanwhile, in bus-type networks, data arrives at each terminal even when the data is unicast.

Thus, in a bus-type network, it is possible to receive a response without sending a request as in IGMP. In other words, each device can acquire necessary data by receiving requests and responses exchanged between other devices. Accordingly, since each device does not send a request by itself, it is possible to reduce used bandwidth. Such a bandwidth reduction method is called a monitoring method. [0007] The monitoring method aims to reduce communication between devices in such a way that, in a bus-type network, each device monitors communication performed between other devices and acquires data the device intends to collect.

However, if the bridge is installed, communication between other devices does not reach each device that performs monitoring. For this reason, each device has to send a request by itself to acquire necessary data. This makes it difficult to achieve the bandwidth consumption reduction effect.

[0008] Hence, in order to achieve the bandwidth consumption reduction effect even when the bridge is installed, it is possible to let the bridge relay all communication by operating the bridge in the “flooding” mode where no filtering is performed.

However, if the bridge is operated in the “flooding” mode, the bandwidth consumption reduction effect brought by filtering cannot be achieved.

Citation List

Patent Literature [0009] Patent Literature 1: Japanese Patent No. 3995469

Summary of Invention

Technical Problem [0010] The present invention aims to reduce used bandwidth by using both the bridge method and the monitoring method.

Solution to Problem [0011] A relay device according to the present invention includes:

a plurality of communication ports;

a storage unit to store a relay table in which a sender address, a relay message type, and a destination port are associated with each other, a frame analysis unit to acquire, when a frame including a sender address and a message arrives at any of the plurality of communication ports, a type of the message included in the frame as an analysis message type; and a relay judgment unit to select, from the relay table, destination ports that correspond to a pair of the sender address included in the frame and a relay message type which is the same as the analysis message type, and select, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the selected destination ports, a destination port which is the same as the communication port at which the frame arrives.

Advantageous Effects of Invention [0012] According to the present invention, it is possible to reduce used bandwidth by using both the bridge method and the monitoring method.

Brief Description of Drawings [0013] [Fig. 1] Fig. 1 is a block diagram of a relay device 100 in an embodiment 1.

[Fig. 2] Fig. 2 is a block diagram of a storage unit 191 in the embodiment 1.

[Fig. 3] Fig. 3 is a block diagram of a first relay table 210 in the embodiment

1.

[Fig. 4] Fig. 4 is a block diagram of a second relay table 220 in the embodiment 1.

[Fig. 5] Fig. 5 is a block diagram of a message correspondence table 230 in the embodiment 1.

[Fig. 6] Fig. 6 is a block diagram of a frame 200 in the embodiment 1.

[Fig. 7] Fig. 7 is a flowchart of a relay method in the embodiment 1.

[Fig. 8] Fig. 8 is a flowchart of a relay learning process (S200) in the embodiment 1.

[Fig. 9] Fig. 9 is a flowchart of a relay judgment process (S300) in the embodiment 1.

[Fig. 10] Fig. 10 is a diagram illustrating a bus-type network in the embodiment 1.

[Fig. 11 ] Fig. 11 is a diagram illustrating the first relay table 210 in the embodiment 1.

[Fig. 12] Fig. 12 is a diagram illustrating the second relay table 220 in the embodiment 1.

[Fig. 13] Fig. 13 is a diagram illustrating the first relay table 210 in the embodiment 1.

[Fig. 14] Fig. 14 is a diagram illustrating the bus-type network in the embodiment 1.

[Fig. 15] Fig. 15 is a diagram illustrating the bus-type network in the embodiment 1.

[Fig. 16] Fig. 16 is a diagram illustrating a relay message list 240 in an embodiment 2.

[Fig. 17] Fig. 17 is a flowchart of a relay judgment process (S300) in the embodiment 2.

[Fig. 18] Fig. 18 is a diagram illustrating a relay message table 250 in the embodiment 2.

[Fig. 19] Fig. 19 is a flowchart of the relay judgment process (S300) in the embodiment 2.

[Fig. 20] Fig. 20 is a flowchart of a relay learning process (S200) in an embodiment 3.

[Fig. 21] Fig. 21 is a flowchart of a relay judgment process (S300) in the embodiment 3.

[Fig. 22] Fig. 22 is a diagram illustrating a bus-type network in the embodiment 3.

[Fig. 23] Fig. 23 is a hardware block diagram of the relay device 100 in the embodiments.

Description of Embodiments [0014] Throughout the embodiments and drawings, the same or equivalent constituents are given the same reference signs. Description for the constituents given the same reference signs are omitted or abbreviated as appropriate.

[0015] Embodiment 1

A relay device 100 will be described based on Figs. 1 to 15. Specifically, the relay device 100 is network equipment called a bridge.

[0016] *** Description of Configuration ***

The configuration of the relay device 100 will be described based on Fig. 1.

The relay device 100 is a computer equipped with hardware such as a processor 901, a memory 902, and multiple network interfaces (903-1, 903-2). These hardware are connected to one another via signal lines.

The network interface 903-1 and the network interface 903-2 are collectively referred to as a network interface 903.

[0017] The processor 901 is an IC (Integrated Circuit) that executes processing and controls other hardware. Specifically, the processor 901 is any of a CPU, DSP, and GPU. CPU is abbreviation of Central Processing Unit, DSP is abbreviation of Digital Signal Processor, and GPU is abbreviation of Graphics Processing Unit.

The memory 902 is a volatile storage. The memory 902 is also referred to as a main storage or a main memory. Specifically, the memory 902 is a RAM (Random Access Memory).

[0018] The network interface 903 is a device that performs communications. Specifically, the network interface 903 is an NIC (Network Interface Card).

A port of the network interface 903-1 is referred to as a communication port 904-1, and a port of the network interface 903-2 is referred to as a communication port 904-2.

The communication port 904-1 is connected to a network 910-1. The communication port 904-2 is connected to a network 910-2 different from the network

910-1.

The communication port 904-1 and the communication port 904-2 are collectively referred to as a communication port 904. The network 910-1 and the network 910-2 are collectively referred to as a network 910.

[0019] The relay device 100 includes “units”, such as a frame analysis unit 110, a relay learning unit 120, and a relay judgment unit 130, as its functional constituents. The functions of these “units” are implemented by software. The functions of the “units” will be described later.

[0020] The OS (Operating System) and programs for implementing the functions of the “units” are loaded into the memory 902 and executed by the processor 901.

The processor 901 executes the programs for implementing the functions of the “units” while executing the OS.

Data acquired by executing the programs for implementing the functions of the “units” is stored in a storage such as the memory 902, a register in the processor 901, and a cache memory in the processor 901.

[0021] The memory 902 functions as a storage unit 191 that stores therein data used, generated, input, output, sent, or received by the relay device 100. Here, another storage may function as the storage unit 191 instead.

The network interface 903 functions as a receiver (192-1, 192-2) that receives data, and as a sender (193-1, 193-2) that sends data.

The receiver 192-1 and the receiver 192-2 are collectively referred to as a receiver 192, and the sender 193-1 and the sender 193-2 are collectively referred to as a sender 193.

[0022] The relay device 100 may include multiple processors instead of the processor 901. The multiple processors together execute the programs for implementing the functions of the “units”.

The programs for implementing the functions of the “units” can be stored in a nonvolatile storage medium such as a magnetic disc, optical disc, and a flash memory so as to be readable by a computer. The nonvolatile storage medium is a nontransitory tangible medium.

A “unit” may be read as “process” or “step” instead. A function of “unit” may be implemented by firmware.

[0023] The configuration of the storage unit 191 is described based on Fig. 2.

The storage unit 191 stores therein a first relay table 210, a second relay table 220, a message correspondence table 230, and the like. These tables will be described later.

[0024] The configuration of the first relay table 210 is described based on Fig. 3.

The first relay table 210 has entries corresponding to records.

The entries of the first relay table 210 are referred to as first relay entries (211-1, 211-2, 211-3). The first relay entries (211-1, 211-2, 211-3) are collectively referred to as a first relay entry 211.

[0025] In the first relay entry 211, a destination address and a destination port are associated with each other.

The destination address is a terminal address to which a frame is sent.

The destination port is the communication port 904 for connection to the network 910 to which the destination terminal is connected. A destination port identifier is set in the column of the destination port. The destination port identifier is an identifier for identifying the destination port.

The first relay entry 211 is registered by the relay learning unit 120 as needed.

[0026] The first relay table 210 corresponds to a filtering database (FDB).

[0027] The configuration of the second relay table 220 is described based on Fig. 4.

The second relay table 220 has entries corresponding to records.

The entries of the second relay table 220 are referred to as second relay entries (221-1, 221-2). The second relay entries (221-1, 221-2) are collectively referred to as a second relay entry 221.

[0028] In the second relay entry 221, a sender address, a relay message type, and a destination port are associated with each other.

The sender address is a terminal address to which a frame is sent.

The relay message type is the type of a message included in a frame. Specifically, the relay message type is a response message. The response message is a message to respond to a request message. The request message is a message to request the response message.

The destination port is the communication port 904 for connection to the network 910 to which the destination terminal of the frame is connected. A destination port identifier is set in the column of the destination port.

The second relay entry 221 is registered by the relay learning unit 120 as needed.

[0029] The second relay table 220 corresponds to an extended FDB.

[0030] The configuration of the message correspondence table 230 is described based on Fig. 5.

The message correspondence table 230 has entries corresponding to records.

The entries of the message correspondence table 230 are referred to as message correspondence entries (231-1 to 231-3). The message correspondence entries (231-1 to 231-3) are collectively referred to as a message correspondence entry

231.

[0031] In the message correspondence entry 231, a first message type and a second message type are associated with each other.

The first message type is the type of a message included in a frame.

Specifically, the first message type is a request message.

The second message type is the type of a message included in a frame.

Specifically, the second message type is a response message.

[0032] The message correspondence table 230 is generated in advance.

[0033] The configuration of a frame 200 is described based on Fig. 6.

The frame 200 includes a sender address 201, a destination address 202, a type 203, a message 204, and the like.

The sender address 201 is the address of a terminal from which the frame

200 is sent.

The destination address 202 is the address of a terminal to which the frame

200 is sent.

The type 203 is the type of the message 204.

The message 204 is a payload. Specifically, the message 204 is a request message or a response message.

[0034] —Description of operation—

The operation of the relay device 100 corresponds to a relay method.

Meanwhile, the procedures of the relay method correspond to the procedures of a relay program.

[0035] The relay method is described based on Fig. 7.

Step S110 is a reception process.

In Step SI 10, when the frame 200 arrives at any of the multiple communication ports 904, the receiver 192 that corresponds to the communication port 904 at which the frame 200 arrives receives the frame 200 having arrived.

The communication port 904 at which the frame 200 arrives is referred to as a reception port.

[0036] Step SI20 is a frame analysis process.

In Step S120, the frame analysis unit 110 analyzes the received frame 200 to obtain the sender address 201, the destination address 202, and an analysis message type.

The analysis message type is the type of the message 204 included in the received frame 200.

[0037] Specifically, the frame analysis unit 110 operates in the following manner.

The frame analysis unit 110 extracts the sender address 201 from the received frame 200.

The frame analysis unit 110 extracts the destination address 202 from the received frame 200.

The frame analysis unit 110 extracts the type 203 from the received frame 200. The extracted type 203 becomes the analysis message type.

Here, if no type 203 is included in the frame 200, the frame analysis unit 110 subjects the message 204 to an analysis algorithm to obtain the analysis message type. The analysis algorithm executed here is an algorithm previously determined for obtaining the analysis message type.

[0038] Further, the frame analysis unit 110 acquires a reception port port identifier from the receiver 192 that corresponds to the reception port. The reception port identifier is an identifier for identifying the reception port.

[0039] Step S200 is a relay learning process.

In Step S200, the relay learning unit 120 registers the first relay entry 211 in the first relay table 210 based on the information acquired in Step S120.

Further, the relay learning unit 120 registers the second relay entry 221 in the second relay table 220 based on the information acquired in Step SI20.

The relay learning process (S200) will be described in detail later.

[0040] Step S300 is a relay judgment process.

In Step S300, the relay judgment unit 130 selects a sending port based on the information acquired in Step S120, the first relay table 210, and the second relay table 220.

The sending port is the communication port 904 to output the received frame

200.

The relay judgment process (S3 00) will be described in detail later.

[0041] Step S130 is a sending process.

In Step SI30, the sender 193 that corresponds to each sending port sends the received frame 200 from the sending port.

Thereby, the received frame 200 is relayed from the network 910 to which the reception port is connected to the network 910 to which the sending port is connected.

However, Step S130 is not executed if no sending port is selected in Step S300.

[0042] The procedures of the relay learning process (S200) are described based on Fig. 8.

In Step S210, the relay learning unit 120 associates the destination address, which is the same as the sender address 201, and the destination port, which is the same as the reception port, with each other to generate the first relay entry 211.

Then, the relay learning unit 120 registers the generated first relay entry 211 in the first relay table 210.

[0043] In Step S221 and Step S222, the relay learning unit 120 judges whether the first message type which is the same as the analysis message type is included in the message correspondence table 230. Specifically, the relay learning unit 120 operates in the following manner.

[0044] In Step S221, the relay learning unit 120 searches the message correspondence table 230 for the message correspondence entry 231 including the first message type which is the same as the analysis message type.

In Fig. 8, the message correspondence entry 231 including the first message type which is the same as the analysis message type is referred to as a relevant entry. [0045] In Step S222, the relay learning unit 120 judges whether the relevant entry exists based on the search result.

If the relevant entry exists, the process proceeds to Step S223.

If no relevant entry exists, no second relay entry 221 is registered and the process terminates.

[0046] In Step S223, the relay learning unit 120 acquires, from the message correspondence table 230, the second message type that corresponds to the first message type which is the same as the analysis message type.

Specifically, the relay learning unit 120 acquires the second message type from the relevant entry.

[0047] In Step S230, the relay learning unit 120 associates the sender address which is the same as the destination address 202, the relay message type which is the same as the second message type acquired in Step S223, and the destination port which is the same as the reception port with one another to generate the second relay entry 221.

Then, the relay learning unit 120 registers the generated second relay entry

221 in the second relay table 220.

[0048] The procedures of the relay judgment process (S3 00) are described based on Fig. 9.

In Step S311 to Step 313, the relay judgment unit 130 selects, from the first relay table 210, the destination port that corresponds to the destination address 202. Specifically, the relay judgment unit 130 operates in the following manner.

[0049] In Step 311, the relay judgment unit 130 searches the first relay table 210 for the first relay entry 211 including the destination address 202.

In Fig. 9, the first relay entry 211 including the destination address 202 is referred to as a first relevant entry.

[0050] In Step S312, the relay judgment unit 130 judges whether the first relevant entry exists based on the search result.

If the first relevant entry exists, the process proceeds to Step S313.

If no relevant entry exists, the process proceeds to Step S340.

[0051] In Step S313, the relay judgment unit 130 acquires the destination port identifier from the first relevant entry.

[0052] In Step S321 to Step S323, the relay judgment unit 130 selects, from the second relay table 220, the destination port that corresponds to the pair of the sender address 201 and the relay message type which is the same as the analysis message type. Specifically, the relay judgment unit 130 operates in the following manner.

[0053] In Step S321, the relay judgment unit 130 searches the second relay table

220 for the second relay entry 221 that includes the sender address 201 and the relay message type which is the same as the analysis message type.

In Fig. 9, the second relay entry 221 including the sender address 201 and the relay message type which is the same as the analysis message type is referred to as a second relevant entry. The second relevant entry is at least one second relay entry 221.

[0054] In Step S322, the relay judgment unit 130 judges whether the second relevant entry exists based on the search result.

If the second relevant entry exists, the process proceeds to Step S323.

If no second relevant entry exists, the process proceeds to Step S330.

[0055] In Step S323, the relay judgment unit 130 acquires the destination port identifier from each second relevant entry.

[0056] In Step S330, the relay judgment unit 130 excludes the destination port, which is the same as the reception port, from the destination port selected in Step S311 to Step S313 and the destination port selected in Step S321 to Step S323.

Thereby, the remaining destination port is selected as the sending port.

[0057] Specifically, the relay judgment unit 130 deletes the reception port identifier from the destination port identifier acquired in Step S313 and the destination port identifier acquired in Step S323.

[0058] In Step S340, the relay judgment unit 130 excludes the reception port from all the communication ports 904.

Thereby, the remaining communication port 904 obtained by excluding the reception port from all the communication ports 904 is selected as the sending port. [0059] The relay learning process (S200) and the relay judgment process (S300) are described specifically based on Fig. 10.

In the bus-type network, the relay device 100 is connected to the network 910-1 and the network 910-2.

A port 1 is the communication port 904-1 and a port 2 is the communication port 904-2.

A terminal B 101 is a terminal connected to the network 910-1. The address of the terminal B 101 is an address B.

A terminal C 102 and a terminal D 103 are terminals connected to the network 910-2. The address of the terminal C 102 is an address C and the address of the terminal D 103 is an address D.

[0060] First, a description is given of the relay learning process (S200) in the case where the terminal C 102 sends an X request frame to the terminal D 103.

The X request frame is the frame 200 including an X request message.

The X request frame arrives at the port 2 via the network 910-2 and is received by the receiver 192-2.

Once the X request frame is received, the frame analysis unit 110 acquires a sender address C, a destination address D, the “X request message”, and the “port 2”. The “X request message” is the type of the X request message, and the “port 2” is the identifier of a reception port 2.

[0061] The relay learning unit 120 uses the sender address C and the “port 2” to register the first relay entry 211-1 in the first relay table 210 as illustrated in Fig. 11 (S210in Fig. 8).

In the first relay entry 211-1, the destination address is the sender address C and the destination port identifier is the “port 2”.

[0062] The relay learning unit 120 selects, from the message correspondence table 230 in Fig. 5, the message correspondence entry 231-1 that includes the first message type which is the same as the “X request message” (S221 and S222 in Fig. 8).

The relay learning unit 120 obtains an “X response message”, which is the second message type, from the selected message correspondence entry 231-1 (S223 in

Fig. 8).

The relay learning unit 120 uses the destination address D, the “X response message”, and the “port 2” to register the second relay entry 221-1 in the second relay table 220 as illustrated in Fig. 12 (S230 in Fig. 8).

In the second relay entry 221-1, the sender address is the destination address D, the relay message type is the “X response message”, and the destination port is the “port 2”.

[0063] Next, a description is given of the relay learning process (S200) in the case where the terminal D 103 sends an X response frame to the terminal C 102.

The X response frame is the frame 200 including an X response message.

In the X response frame, the sender address 201 is the address D and the destination address 202 is the address C.

The X response frame arrives at the port 2 via the network 910-2 and is received by the receiver 192-2.

Once the X response frame is received, the frame analysis unit 110 acquires a sender address D, a destination address C, the “X response message”, and the “port 2”. The “X response message” is the type of the X response message.

[0064] The relay learning unit 120 uses the sender address D and the “port 2” to register the first relay entry 211-2 in the first relay table 210 as illustrated in Fig. 13 (S210 in Fig. 8).

In the first relay entry 211-2, the destination address is the sender address D and the destination port identifier is the “port 2”.

[0065] The relay learning unit 120 searches the message correspondence table 230 in Fig. 5 for the message correspondence entry 231 that includes the first message type which is the same as the “X response message” (S221 in Fig. 8). However, since no relevant message correspondence entry 231 exists, the relay learning unit 120 does not register the second relay entry 221 (S222 in Fig. 8).

[0066] Next, a description is given of the relay judgment process (S300) in the case where the terminal C 102 newly sends the X request frame to the terminal D 103.

The first relay table 210 is in a state illustrated in Fig. 13 and the second relay table

220 is in a state illustrated in Fig. 12.

[0067] The relay judgment unit 130 selects, from the first relay table 210 in Fig. 13, the first relay entry 211-2 that includes the destination address D (S311 and S312 in Fig. 9).

The relay judgment unit 130 acquires the “port 2”, which is the destination port identifier, from the selected first relay entry 211-2 (S313 in Fig. 9).

[0068] The relay judgment unit 130 searches the second relay table 220 in Fig. 12 for the second relay entry 221 that corresponds to the pair of the sender address C and the “X request message” (S321 in Fig. 9). However, no relevant second relay entry

221 exists (S322 in Fig. 9).

[0069] The relay judgment unit 130 deletes the “port 2”, which is the identifier of the reception port 2, from the “port 2” which is the acquired destination port identifier (S330 in Fig. 9).

As a result, the acquired destination port identifier disappears, and thus no sending port is selected and the X request frame is not relayed.

[0070] Next, a description is given of the relay judgment process (S300) in the case where the terminal D 103 newly sends the X response frame to the terminal C 102.

The first relay table 210 is in a state illustrated in Fig. 13 and the second relay table 220 is in a state illustrated in Fig. 12.

[0071] The relay judgment unit 130 selects, from the first relay table 210 in Fig. 13, the first relay entry 211-1 that includes the destination address C (S311 and S312 in Fig. 9).

The relay judgment unit 130 acquires the “port 2”, which is the destination port identifier, from the selected first relay entry 211-1 (S313 in Fig. 9).

[0072] The relay judgment unit 130 selects, from the second relay table 220 in Fig. 12, the second relay entry 221-1 that corresponds to the pair of the sender address D and the “X response message” (S321 and S322 in Fig. 12).

The relay judgment unit 130 acquires the “port 2”, which is the destination port identifier, from the selected second relay entry 221-1 (S323 in Fig. 9).

[0073] The relay judgment unit 130 deletes the “port 2”, which is the identifier of the reception port 2, from the “port 2” which is the acquired destination port identifier.

As a result, the acquired destination port identifier disappears, and thus no sending port is selected and the X response frame is not relayed.

[0074] As described above, the frame 200 communicated between the terminal C

102 and the terminal D 103 in the network 910-2 is not relayed to the network 910-1. Thereby, the bandwidth consumption of the network 910-1 can be reduced.

[0075] The relay learning process (S200) is described in detail based on Fig. 14.

The configuration of the bus-type network is the same as that in Fig. 10. The first relay table 210 is in a state illustrated in Fig. 13 and the second relay table 220 is in a state illustrated in Fig. 12.

The terminal B 101 sends an X request frame to the terminal D 103.

The X request frame arrives at the port 1 via the network 910-1 and is received by the receiver 192-1.

Once the X request frame is received, the frame analysis unit 110 acquires the sender address B, the destination address D, the “X request message”, and the “port

1”. The “port 1” is the identifier of the reception port 1.

[0076] The relay learning unit 120 uses the sender address B and the “port 1” to register the first relay entry 211-3 in the first relay table 210 as illustrated in Fig. 3 (S210in Fig. 8).

In the first relay entry 211-3, the destination address is the sender address B and the destination port is the “port 1”.

[0077] The relay learning unit 120 selects, from the message correspondence table 230 in Fig. 5, the message correspondence entry 231-1 that includes the first message type which is the same as the “X request message” (S221 and S222 in Fig. 8).

The relay learning unit 120 acquires the “X response message”, which is the second message type, from the selected message correspondence entry 231-1 (S223 in Fig. 8).

The relay learning unit 120 uses the destination address D, the “X response message”, and the “port 1” to register the second relay entry 221-2 in the second relay table 220 as illustrated in Fig. 4 (S230 in Fig. 8).

In the second relay entry 221-2, the sender address is the destination address D, the relay message type is the “X response message”, and the destination port is the “port 1”.

[0078] Here, the relay device 100 relays, by its typical relay function, the X request frame to the network 910-2 through the port 2. The X request frame is then received by the terminal D 103.

Then, the terminal D 103 sends an X response frame to the terminal B 101 and the X response frame arrives at the port 2 via the network 910-2. The relay device 100 thereafter relays, by its typical relay function, the X response frame to the network 910-1. Then, the X response frame is received by the terminal B 101.

[0079] The relay judgment process (S300) is described in detail based on Fig. 15. The configuration of the bus-type network is the same as that in Fig. 10. The first relay table 210 is in a state illustrated in Fig. 3 and the second relay table 220 is in a state illustrated in Fig. 4.

[0080] First, a description is given of the case where the terminal C 102 sends an X request frame to the terminal D 103.

The relay judgment unit 130 selects, from the first relay table 210 in Fig. 3, the first relay entry 211-2 that includes the destination address D (S311 and S312 in Fig. 9).

[0081] The relay judgment unit 130 searches the second relay table 220 in Fig. 4 for the second relay entry 221 that corresponds to the pair of the sender address C and the “X request message” (S321 in Fig. 9). However, no relevant second relay entry 221 exists (S322 in Fig. 9).

[0082] The relay judgment unit 130 deletes the “port 2”, which is the identifier of the reception port 2, from the “port 2” which is the acquired destination port identifier.

[0083] Next, a description is given of the case where the terminal D 103 sends an X response frame to the terminal C 102.

The relay judgment unit 130 selects, from the first relay table 210 in Fig. 3, the first relay entry 211-1 that includes the destination address C (S311 and S312 in Fig. 9).

[0084] The relay judgment unit 130 selects, from the second relay table 220 in Fig. 4, the second relay entry 221-1 and the second relay entry 221-2 that correspond to the pair of the sender address D and the “X response message” (S321 and S322 in Fig. 9).

The relay judgment unit 130 acquires the “port 2”, which is the destination port identifier, from the selected second relay entry 221-1, and acquires the “port 1”, which is the destination port identifier, from the selected second relay entry 221-2. [0085] The relay judgment unit 130 deletes the “port 2”, which is the identifier of the reception port 2, from the “port 1” and the “port 2” which are the acquired destination port identifiers.

As a result, the “port 1” remains among the acquired destination port identifiers, and thus the port 1 is selected as the sending port. Then, the X response frame is relayed to the network 910-1 by the sender 193-1 and received by the terminal B 101.

The terminal B 101 can acquire the X response message from the relayed X response frame by the monitoring function.

[0086] As described above, the terminal B 101 can receive the X response frame and acquire the X response message without sending an X request frame by itself. Thereby, the bandwidth consumption of the network 910-1 can be reduced.

[0087] *** Effect of Embodiment 1 ***

It is possible to reduce used bandwidth by using both the bridge method and the monitoring method.

[0088] For example, the embodiment exhibits the following effect in an air-conditioning system.

In Fig. 10, the terminal B 101 is an air-conditioning controller, the terminal

D 103 is a temperature sensor, and the terminal C 102 is an indoor device.

The air-conditioning controller is a computer designed to perform air-conditioning control by acquiring temperature information periodically.

In the air-conditioning system described above, when the indoor device sends and receives a request frame and a response frame with the temperature sensor periodically in order to acquire temperature information, the relay device 100 relays the response frame to the air-conditioning controller periodically.

This enables the air-conditioning controller to acquire temperature information from the periodically relayed response frame without sending a request frame periodically by itself.

[0089] Further, the relay device 100 does not relay a request frame to the air-conditioning controller if the air-conditioning controller has no need to receive it. Thereby, the bandwidth consumption of the network 910-1 can be reduced.

[0090] In this way, it is possible to use both the bridge method and the monitoring method at the same time and achieve the bandwidth consumption reduction effect brought by both of them.

[0091] *** Other Configurations ***

The number of each of the network interface 903 and the communication port 904 may be three or more.

[0092] The second relay table 220 that corresponds to an extended FDB may have an ageing function as in the case of a typical FDB. In other words, the relay learning unit 120 may delete the second relay entry 221 if the second relay table 220 is not updated for a predetermined period of time.

[0093] The message correspondence table 230 may be partially or wholly set by an external server dynamically. Alternatively, the relay learning unit 120 may register the message correspondence entry 231 in the message correspondence table 230 by monitoring relay frames and learning the correspondence relation between messages. [0094] Addresses registered in the first relay table 210 and the second relay table 220 may be an address used for frame transmission or may be the logical address of a terminal. If IP communication through Ethernet (registered trademark) commonly frequently used is taken as an example, an address registered in the first relay table 210 that corresponds to an FDB may be a MAC address, and an address registered in the second relay table 220 that corresponds to an extended FDB may be an IP address. IP is abbreviation of Internet Protocol, and MAC is abbreviation of Media Access Control.

[0095] Embodiment 2

A mode of judging whether the frame 200 needs to be relayed or not using a relay message type list is described based on Fig. 16 to Fig. 19 mainly in terms of points different from the embodiment 1.

[0096] *** Description of Configuration ***

The configuration of the relay device 100 is the same as that in Fig. 1 of the embodiment 1.

However, a relay message list 240 is stored in the storage unit 191.

As illustrated in Fig. 16, the relay message list 240 is a list including a relay message type. The relay message list 240 is generated in advance.

How to use the relay message list 240 will be described later.

[0097] *** Description of Operation ***

The procedures of the relay method are the same as those in Fig. 7 of the embodiment 1.

However, a part of the procedures of the relay judgment process (S300) differs from that of the embodiment 1.

[0098] The procedures of the relay judgment process (S300) are described based on Fig. 17.

Step S311 to Step S340 are the same as those in Fig. 9 of the embodiment 1.

Step S351 and Step S352 are added processes. Step S351 and Step S352 are described below.

[0099] In Step S351, the relay judgment unit 130 searches the relay message list 240 for the relay message type which is the same as the analysis message type.

[0100] In Step S352, based on the search result, the relay judgment unit 130 judges whether the relay message list 240 includes the relay message type which is the same as the analysis message type.

If the relay message list 240 includes the relay message type which is the same as the analysis message type, the process proceeds to Step S340.

If the relay message list 240 includes no relay message type which is the same as the analysis message type, the process proceeds to Step S321.

[0101] Accordingly, if the relay message list 240 includes the relay message type which is the same as the analysis message type, the remaining communication port 904 obtained by excluding the reception port from all the communication ports 904 is selected as the sending port.

If the relay message list 240 includes no relay message type which is the same as the analysis message type, as in the case of the embodiment 1, the remaining destination port obtained by excluding the reception port from the destination ports selected from the first relay table 210 and the second relay table 220 is selected as the sending port.

[0102] The relay judgment process (S300) is described specifically based on Fig.

10.

The first relay table 210 is in a state illustrated in Fig. 11.

[0103] First, a description is given of the case where the terminal C 102 sends an X request frame to the terminal D 103.

The relay judgment unit 130 searches the first relay table 210 in Fig. 11 for the first relay entry 211-2 that includes the destination address D (S311 in Fig. 17). However, no relevant first relay entry 211 exists (S312 in Fig. 17).

[0104] The relay judgment unit 130 excludes the reception port 2 from all the communication ports 904 (S340 in Fig. 17).

As a result, the port 1 is selected as the sending port. Then, the X request frame is relayed to the network 910-1 by the sender 193-1.

[0105] Next, a description is given of the case where the terminal D 103 sends an X response frame to the terminal C 102.

The relay judgment unit 130 selects, from the first relay table 210 in Fig. 11, the first relay entry 211-1 that includes the destination address C (S311 and S312 in Fig. 17).

The relay judgment unit 130 acquires the “port 2”, which is the destination port identifier, from the selected first relay entry 211-1 (S313 in Fig. 17).

[0106] The relay judgment unit 130 searches the relay message list 240 in Fig. 16 for the “X response message” (S351 in Fig. 17). The relay message list 240 in Fig.

includes the “X response message” (S352 in Fig. 17).

[0107] The relay judgment unit 130 excludes the reception port 2 from all the communication ports 904 (S340 in Fig. 17).

As a result, the port 1 is selected as the sending port. Then, the X response frame is relayed to the network 910-1 by the sender 193-1 and received by the terminal

B 101.

[0108] *** Effect of Embodiment 2 ***

Since messages which are likely to be referenced are registered in the relay message list 240, it is possible to reduce periodical sending of request messages and reduce the bandwidth consumption of the network 910.

[0109] The mode not using the second relay table 220 may be employed.

Specifically, Step S221 to Step S230 in Fig. 8 and Step S321 to Step S323 in Fig. 9 may be omitted.

Thereby, the processing load of the relay device 100 can be reduced.

[0110] * * * Other Configurations * * *

A relay message table 250 may be used instead of the relay message list 240. [0111] The configuration of the relay message table 250 is described based on Fig. 18.

The relay message table 250 has entries that correspond to records.

The entries of the relay message table 250 are referred to as relay message entries (251-1, 251-2). The relay message entries (251-1, 251-2) are collectively referred to as a relay message entry 251.

In the relay message entry 251, a relay message identifier and a destination port are associated with each other. A destination port identifier is set in the column of the destination port.

The relay message table 250 is generated in advance.

[0112] The relay judgment process (S300) in the case of using the relay message table 250 is described based on Fig. 19.

Step S311 to Step S340 are the same as those in Fig. 9 of the embodiment 1.

Step S361 to Step S363 are added processes. Step S361 to Step S363 are described below.

[0113] In Step S361 to Step S363, the relay judgment unit 130 selects the destination port corresponding to the analysis message type from the relay message table 250. Specifically, the relay judgment unit 130 operates in the following manner. [0114] In Step S361, the relay judgment unit 130 searches the relay message table 250 for the relay message entry 251 that includes the relay message type which is the same as the analysis message type.

In Fig. 19, the relay message entry 251 including the relay message type which is the same as the analysis message type is referred to as a third relevant entry. [0115] In Step S362, the relay judgment unit 130 judges whether the third relevant entry exists based on the search result.

If the third relevant entry exists, the process proceeds to Step S363.

If no third relevant entry exists, the process proceeds to Step S321. [0116] In Step S3 63, the relay judgment unit 130 acquires the destination port identifier from the third relevant entry.

After Step S363 is over, the process proceeds to Step S330.

[0117] In Step S330 after Step S363, the relay judgment unit 130 excludes the destination port, which is the same as the reception port, from the destination port selected in Step S361 to Step S363.

Thereby, the remaining destination port is selected as the sending port. [0118] Embodiment 3

A mode of judging whether the frame 200 needs to be relayed or not based on the transmission bandwidth of the communication port 904 is described based on

Fig. 20 to Fig. 22 mainly in terms of points different from the embodiment 1.

[0119] *** Description of Configuration ***

Here, the transmission bandwidths of all the respective communication ports 904 and a reference bandwidth are stored in the storage unit 191 in advance. The reference bandwidth is a reference transmission bandwidth. The transmission bandwidth of each communication port 904 is the transmission bandwidth of the network 910 to which the communication port 904 is connected. The transmission bandwidth corresponds to a transmission speed.

[0120] *** Description of Operation ***

However, a part of the procedures of the relay learning process (S200) and a part of the procedures of the relay judgment process (S300) differ from those of the embodiment 1.

[0121] The procedures of the relay learning process (S200) are described based on Fig. 20.

Step S210 and Step S221 to Step S230 are the same as those in Fig. 8 of the embodiment 1.

Step S220 is a process added to Fig. 8 of the embodiment 1. Step S220 is described below.

[0122] In Step S220, the relay judgment unit 130 judges whether registration is needed or not based on the transmission bandwidth of the reception port.

Specifically, the relay judgment unit 130 compares the transmission bandwidth of the reception port with the reference bandwidth.

If the transmission bandwidth of the reception port is equal to or larger than the reference bandwidth (registration is not needed), the process terminates.

If the transmission bandwidth of the reception port is smaller than the reference bandwidth (registration is needed), the process proceeds to Step S221. [0123] Accordingly, if the transmission bandwidth of the reception port is equal to or larger than the reference bandwidth, the second relay entry 221 is not registered. [0124] The procedures of the relay judgment process (S3 00) are described based on Fig. 21.

Step S311 to Step S330 are the same as those in Fig. 9 of the embodiment 1.

Step S310 is an added process. Step S310 is described below.

[0125] In Step S310, the relay judgment unit 130 judges whether narrowing down is needed or not based on the transmission bandwidth of the remaining communication port 904 excluding the reception port.

Specifically, for each communication port 904 excluding the reception port, the relay judgment unit 130 compares the transmission bandwidth of the communication port 904 with the reference bandwidth.

Then, the relay judgment unit 130 judges whether a low-bandwidth port exists excluding the reception port. The low-bandwidth port is the communication port 904 with a transmission bandwidth smaller than the reference bandwidth.

If the low-bandwidth port exists (narrowing down is needed), the process proceeds to Step S311.

If no low-bandwidth port exists (narrowing down is not needed), the process proceeds to Step S340.

[0126] Accordingly, if no low-bandwidth port exists, the remaining communication port 904 excluding the reception port is selected as the sending port.

[0127] The relay learning process (S200) and the relay judgment process (S300) are described specifically based on Fig. 22.

In the bus-type network, there are two relay devices (100-1, 100-2). The relay device 100-1 and the relay device 100-2 are collectively referred to as the relay device 100.

[0128] The relay device 100-1 is connected to a network 911 and a network 912.

In the relay device 100-1, a port 1 is connected to the network 911 and a port 2 is connected to the network 912. The transmission bandwidth of the network 911 and the port 1 is β bps (bits per second). The transmission bandwidth of the network 912 and the port 2 is a bps.

[0129] The relay device 100-2 is connected to the network 912 and a network 913. In the relay device 100-2, a port 1 is connected to the network 912 and a port 2 is connected to the network 913. The transmission bandwidth of the network 912 and the port 1 is a bps. The transmission bandwidth of the network 913 and the port 2 is β bps.

[0130] A terminal A 104 is a terminal connected to the network 911. AterminalE 105 is a terminal connected to the network 912. A terminal C 102 and a terminal D 103 are terminals connected to the network 913.

The network 911, the network 912, and the network 913 are collectively referred to as the network 910.

[0131] a is a value sufficiently larger than β.

In other words, the transmission bandwidth a of the network 912 is sufficiently larger than the transmission bandwidth β of the network 911 and the network 913.

The reference bandwidth is a value equal to or larger than β and smaller than a.

[0132] For example, in air-conditioning systems and building systems, the transmission bandwidth of a network to which end devices are connected is sometimes set low in order to prioritize lay-down efficiency and low cost. On the other hand, a central network to which a controller that integrally controls a system or a host system is connected sometimes has enough transmission bandwidth.

[0133] First, a description is given of the relay learning process (S200) in the relay device 100-2 in the case where the terminal E 105 sends an X request frame to the terminal D 103.

The X request frame arrives at the port 1 via the network 912 and is received by the receiver 192-1. The transmission bandwidth of the port 1 is a bps.

Once the X request frame is received, the frame analysis unit 110 acquires a sender address E, a destination address D, the “X request message”, the “port 1”, and a transmission bandwidth a.

[0134] The relay learning unit 120 registers, in the first relay table 210, the first relay entry 211 that includes the sender address E as the destination address and the “port 1” as the destination port identifier (S210 in Fig. 20).

[0135] The relay learning unit 120 compares the transmission bandwidth a with the referenced bandwidth (S220 in Fig. 20).

Since the transmission bandwidth a is equal to or larger than the reference bandwidth, the second relay entry 221 is not registered (S221 to S230 in Fig. 20). [0136] Next, a description is given of the relay learning process (S200) in the relay device 100-2 in the case where the terminal C 102 sends an X request frame to the terminal D 103.

The X request frame arrives at the port 2 via the network 913 and is received by the receiver 192-2. The transmission bandwidth of the port 2 is β bps.

Once the X request frame is received, the frame analysis unit 110 acquires a sender address C, a destination address D, the “X request message”, the “port 2”, and a transmission bandwidth β.

[0137] The relay learning unit 120 registers, in the first relay table 210, the first relay entry 211 that includes the sender address C as the destination address and the “port 2” as the destination port identifier (S210 in Fig. 8).

[0138] The relay learning unit 120 compares the transmission bandwidth β with the reference bandwidth (S220 in Fig. 20).

Since the transmission bandwidth β is smaller than the reference bandwidth, the second relay entry 221 is registered (S221 to S230 in Fig. 20).

[0139] Next, a description is given of the relay judgment process (S300) in the relay device 100-2 in the case where the terminal C 102 sends an X request frame to the terminal D 103.

The relay judgment unit 130 compares the transmission bandwidth a of the port 1 with the reference bandwidth while excluding the reception port 2. Since the transmission bandwidth a is equal to or larger than the reference bandwidth, the port 1 is not a low-bandwidth port (S310 in Fig. 21).

The relay judgment unit 130 excludes the reception port 2 from all the communication ports 904 (S340 in Fig. 21).

As a result, the port 1 is selected as the sending port. Then, the X request frame is relayed to the network 912 by the sender 193-1.

[0140] Next, a description is given of the relay judgment process (S300) in the relay device 100-2 in the case where the terminal D 103 sends an X response frame to the terminal C 102.

The X response frame arrives at the port 2 via the network 913 and is received by the receiver 192-2. The transmission bandwidth of the port 2 is β bps.

Once the X response frame is received, the frame analysis unit 110 acquires a sender address D, a destination address C, the “X response message”, the “port 2”, and a transmission bandwidth β.

[0141] The relay judgment unit 130 compares the transmission bandwidth a of the port 1 with the reference bandwidth while excluding the reception port 2. Since the transmission bandwidth a is equal to or larger than the reference bandwidth, the port 1 is not a low-bandwidth port (S310 in Fig. 21).

As a result, the port 1 is selected as the sending port. Then, the X request frame is relayed to the network 912 by the sender 193-1 and received by the terminal E 105.

The terminal E 105 can acquire the X response message from the relayed X response frame by the monitoring function.

[0142] *** Effect of Embodiment 3 ***

By omitting the learning of the second relay table 220 and the relay judgment using the second relay table 220 for networks with a wide transmission bandwidth, the processing load of the relay device 100 can be reduced.

Since the frame 200 is not relayed to the network 910 with a narrow transmission bandwidth, the bandwidth consumption of the network 910 with a narrow transmission bandwidth can be reduced.

The network 910 with a wide transmission bandwidth can achieve the bandwidth consumption reduction effect by using the monitoring method of the terminal.

[0143] *** Other Configurations ***

Instead of the transmission bandwidth of the reception port, it is also possible to compare a bandwidth difference between the reception port and the sending port or the bandwidth ratio of the reception port to the sending port with the reference bandwidth. The bandwidth difference is the difference in transmission bandwidth and the bandwidth ratio is the ratio of the transmission bandwidth.

[0144] *** Supplement of Embodiments ***

In the embodiments, the function of the relay device 100 may be implemented by hardware.

Fig. 23 illustrates the configuration of the relay device 100 in the case where its function is implemented by hardware.

The relay device 100 includes a processing circuit 990. The processing circuit 990 is also referred to as a processing circuitry.

The processing circuit 990 is an electronic circuit dedicated to implement the functions of the “units” such as the frame analysis unit 110, the relay learning unit 120, the relay judgment unit 130, and the storage unit 191.

Specifically, the processing circuit 990 is any of a single circuit, a complex circuit, a processor implemented as a program, a processor implemented as a parallel program, a logic IC, a GA, an ASIC, and an FPGA, or a combination of these. GA is abbreviation of Gate Array, ASIC is abbreviation of Application Specific Integrated Circuit, and FPGA is abbreviation of Field Programmable Gate Array.

[0145] The relay device 100 may include multiple processing circuits instead of the processing circuit 990. The multiple processing circuits together have the functions of the “units”.

[0146] The function of the relay device 100 may be implemented by a combination of software and hardware. Specifically, the device may be configured so that a part of the functions of the “units” is implemented by software and the remaining part of the functions of the “units” is implemented by hardware.

[0147] The embodiments are shown to exemplify preferable modes and not to limit the technical scope of the present invention. The embodiments may be implemented partially, or may be implemented in combination with another mode. The procedures described using the flowcharts etc. may be changed as needed.

Reference Signs List [0148] 100: relay device, 101: terminal B, 102: terminal C, 103: terminal D, 104:

terminal A, 105: terminal E, 110: frame analysis unit, 120: relay learning unit, 130: relay judgment unit, 191: storage unit, 192: receiver, 193: sender, 200: frame, 201: sender address, 202: destination address, 203: type, 204: message, 210: first relay table, 211: first relay entry, 220: second relay table, 221: second relay entry, 230: message correspondence table, 231: message correspondence entry, 240: relay message list, 250: relay message table, 251: relay message entry, 901: processor, 902: memory, 903: network interface, 904: communication port, 910, 911, 912, 913: network, 990: processing circuit.

Claims

[Claim 1] A relay device comprising:

a plurality of communication ports;

a storage unit to store a relay table in which a sender address, a relay message type, and a destination port are associated with each other, a frame analysis unit to acquire, when a frame including a sender address and a message arrives at any of the plurality of communication ports, a type of the message included in the frame as an analysis message type; and a relay judgment unit to select, from the relay table, destination ports that correspond to a pair of the sender address included in the frame and a relay message type which is the same as the analysis message type, and select, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the selected destination ports, a destination port which is the same as the communication port at which the frame arrives.
[Claim 2] The relay device according to claim 1, wherein the frame includes a destination address, the storage unit stores a message correspondence table in which a first message type and a second message type are associated with each other, and the relay device comprises a relay learning unit to: judge whether a first message type which is the same as the analysis message type is included in the message correspondence table; acquire, when the first message type which is the same as the analysis message type is included in the message correspondence table, a second message type corresponding to the first message type which is the same as the analysis message type from the message correspondence table; and register, in the relay table, a sender address which is the same as the destination address included in the frame, a relay message type which is the same as the second message type acquired from the message correspondence table, and a destination port which is the same as the communication port at which the frame arrives while associating them with each other.
[Claim 3] The relay device according to claim 1, wherein the frame includes a destination address, the storage unit stores the relay table as a second relay table and stores a first relay table in which a destination address and a destination port are associated with each other, and the relay judgment unit selects, from the first relay table, a destination port that corresponds to the destination address included in the frame, and select, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the destination port selected from the first relay table and the destination port selected from the second relay table, a destination port which is the same as the communication port at which the frame arrives.
[Claim 4] The relay device according to claim 3, wherein the relay device comprises a relay learning unit to register, in the first relay table, a destination address which is the same as the sender address included in the frame and a destination port which is the same as the communication port at which the frame arrives while associating them with each other.
[Claim 5] The relay device according to claim 1, wherein the storage unit stores a relay message list that includes a relay message type, and the relay judgment unit judges whether the relay message type which is the same as the analysis message type is included in the relay message list, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the plurality of communication ports, the communication port at which the frame arrives if the relay message type which is the same as the analysis message type is included in the relay message list, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the destination ports selected from the relay table, a destination port which is the same as the communication port at which the frame arrives if the relay message type which is the same as the analysis message type is not included in the relay message list.
[Claim 6] The relay device according to claim 1, wherein the storage unit stores a relay message table in which a relay message type and a destination port are associated with each other, and the relay judgment unit judges whether the relay message type which is the same as the analysis message type is included in the relay message table, and selects, from the relay message table, the destination ports that correspond to the relay message type which is the same as the analysis message type and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the selected destination ports, a destination port which is the same as the communication port at which the frame arrives if the relay message type which is the same as the analysis message type is included in the relay message table, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the destination ports selected from the relay table, a destination port which is the same as the communication port at which the frame arrives if the relay message type which is the same as the analysis message type is not included in the relay message table.
[Claim 7] The relay device according to claim 2, wherein the relay learning unit judges whether registration is needed or not based on a transmission bandwidth of the communication port at which the frame arrives, and registers, in the relay table, a sender address which is the same as the destination address included in the frame, a relay message type which is the same as the second message type acquired from the message correspondence table, and a destination port which is the same as the communication port at which the frame arrives while associating them with each other if judging that registration is needed.
[Claim 8] The relay device according to claim 1, wherein the relay judgment unit judges whether narrowing down is needed or not based on a transmission bandwidth of a remaining communication port obtained by excluding, from the plurality of communication ports, the communication port at which the frame arrives, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the destination ports selected from the relay table, a destination port which is the same as the communication port at which the frame arrives if judging that narrowing down is needed, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the plurality of communication ports, the communication port at which the frame arrives if judging that narrowing down is not needed.
[Claim 9] The relay device according to claim 3,

5 wherein the relay judgment unit judges whether narrowing down is needed or not based on a transmission bandwidth of a remaining communication port obtained by excluding, from the plurality of communication ports, the communication port at which the frame arrives, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the destination

10 port selected from the first relay table and the destination port selected from the second relay table, a destination port which is the same as the communication port at which the frame arrives if judging that narrowing down is needed, and selects, as a communication port through which to output the frame, a remaining destination port obtained by excluding, from the plurality of communication ports, the communication

15 port at which the frame arrives if judging that narrowing down is not needed.